The present invention relates to an asphalt/polyol emulsion to be used as a water-proofing material, a floor material and the like in various fields, and a process for the preparation of this asphalt/polyol emulsion.
In general, asphalt is often used as a material for the production of a water-proofing material, a floor material and the like. The reason is that asphalt is much cheaper than other polymeric substances, has a very strong binding force and is excellent in water-proofness, softness, water resistance and chemical resistance. However, asphalt is poor in the resistance to high temperature, and because of this defect, asphalt is used only in the civil engineering and construction industry.
The demand for asphalt is great in the civil engineering and construction industry, but in other industrial fields, the consumption of asphalt is very small because asphalt is softened at a high temperature as pointed out above and the coating strength is low.
Accordingly, modification of asphalt with a polymeric substance has been recently considered. For example, urethanized asphalt can be mentioned, and an asphalt/polyol emulsion can be mentioned as the material of urethanized asphalt.
As the urethanized asphalt, there can be mentioned a product formed by impregnating a urethane foam with an asphalt emulsion or cutback asphalt, and a urethanized asphalt foam obtained by mixing a polyol, an isocyanate and an asphalt emulsion and causing a chemical reaction in the mixture.
In view of the water-proofness of urethanized asphalt as described above, non-foamed urethanized asphalt is preferred. However, in order to obtain non-foamed urethanized asphalt, it is necessary to control generation of a gas in the urethane-forming chemical reaction by some means or other.
An isocyanate and a polyol are considered as the prepolymer of polyurethane. There is a technique of forming an emulsion of asphalt and an isocyanate, but a very strict quality control is necessary for this emulsion. Namely, the kind of asphalt that can be used is restricted and very strict previous check is necessary for asphalt.
It is considered that such a strict quality control as that described above will not be necessary for an emulsion of asphalt and a polyol. However, mixing of asphalt with a polyol is generally difficult, and even if softened asphalt (cutback asphalt) is mixed with a polyol, asphalt separates from the polyol because of a poor compatibility, and even if asphalt is dispersed in the polyol with the aid of a surface active agent, phase separtion is caused in a short time.